1use base2k::{Module, Scalar, SvpPPol, VecZnx, VecZnxBig, VecZnxDft, FFT64};
 2use itertools::izip;
 3use sampling::source::Source;
 4
 5fn main() {
 6    let n: usize = 16;
 7    let log_base2k: usize = 18;
 8    let limbs: usize = 3;
 9    let log_scale: usize = (limbs - 1) * log_base2k - 5;
10    let module: Module = Module::new::<FFT64>(n);
11
12    let mut carry: Vec<u8> = vec![0; module.vec_znx_big_normalize_tmp_bytes()];
13
14    let seed: [u8; 32] = [0; 32];
15    let mut source: Source = Source::new(seed);
16
17    let mut res: VecZnx = VecZnx::new(n, log_base2k, limbs);
18
19    // s <- Z_{-1, 0, 1}[X]/(X^{N}+1)
20    let mut s: Scalar = Scalar::new(n);
21    s.fill_ternary_prob(0.5, &mut source);
22
23    // Buffer to store s in the DFT domain
24    let mut s_ppol: SvpPPol = module.svp_new_ppol();
25
26    // s_ppol <- DFT(s)
27    module.svp_prepare(&mut s_ppol, &s);
28
29    // a <- Z_{2^prec}[X]/(X^{N}+1)
30    let mut a: VecZnx = VecZnx::new(n, log_base2k, limbs);
31    a.fill_uniform(&mut source, log_base2k * limbs);
32
33    // Scratch space for DFT values
34    let mut buf_dft: VecZnxDft = module.new_vec_znx_dft(a.limbs());
35
36    // Applies buf_dft <- s * a
37    module.svp_apply_dft(&mut buf_dft, &s_ppol, &a);
38
39    // Alias scratch space
40    let mut buf_big: VecZnxBig = buf_dft.as_vec_znx_big();
41
42    // buf_big <- IDFT(buf_dft) (not normalized)
43    module.vec_znx_idft_tmp_a(&mut buf_big, &mut buf_dft, a.limbs());
44
45    let mut m: VecZnx = VecZnx::new(n, log_base2k, 2);
46
47    let mut want: Vec<i64> = vec![0; n];
48    want.iter_mut()
49        .for_each(|x| *x = source.next_u64n(16, 15) as i64);
50
51    // m
52    m.from_i64(&want, 4, log_scale);
53    m.normalize(&mut carry);
54
55    // buf_big <- m - buf_big
56    module.vec_znx_big_sub_small_a_inplace(&mut buf_big, &m);
57
58    // b <- normalize(buf_big) + e
59    let mut b: VecZnx = VecZnx::new(n, log_base2k, limbs);
60    module.vec_znx_big_normalize(&mut b, &buf_big, &mut carry);
61    b.add_normal(&mut source, 3.2, 19.0, log_base2k * limbs);
62
63    //Decrypt
64
65    // buf_big <- a * s
66    module.svp_apply_dft(&mut buf_dft, &s_ppol, &a);
67    module.vec_znx_idft_tmp_a(&mut buf_big, &mut buf_dft, b.limbs());
68
69    // buf_big <- a * s + b
70    module.vec_znx_big_add_small_inplace(&mut buf_big, &b);
71
72    // res <- normalize(buf_big)
73    module.vec_znx_big_normalize(&mut res, &buf_big, &mut carry);
74
75    // have = m * 2^{log_scale} + e
76    let mut have: Vec<i64> = vec![i64::default(); n];
77    res.to_i64(&mut have, res.limbs() * log_base2k);
78
79    let scale: f64 = (1 << (res.limbs() * log_base2k - log_scale)) as f64;
80    izip!(want.iter(), have.iter())
81        .enumerate()
82        .for_each(|(i, (a, b))| {
83            println!("{}: {} {}", i, a, (*b as f64) / scale);
84        })
85}